Apparatus for forming joggles



May 12, 1,959 JELlNEK 2,886,092

I APPARATUS FR FORMING JOGGLES Filed May l2, 1954 4 Sheets-Sheet 1 .ign-i1 A /o /z/ 2a sa ,/00 /oa /06 /o M www fold May 12, 1959 L. JELNEK 2,886,092

APPARATUS Fox FORMING JoGGLEs Filed May 12, 1954 4 sheets-sheetV 2 E; i- BY lez, #1% l d May 12, 1959 JEUNEK 2,886,092

APPARATUS FOR FORMING JOGGLES Filed May 12, 1954 4 4Sheets-5h99?. 3

May 12, 1959 L. .JELJNEK APPARATUS FOR FORMING JOGGLES 4 shets-sneet 4 Filed May v12, 1954 l sa ...ILE

JNVENTOR. Awf/vcf a /A/f/f BY A Tra/Wvg@ 2,886,092 Patented May 12, 1959 ice APPARATUS FOR FORMING JOGGLES Lawrence JelinelgMount Clemens, Mich.

Application May 12, 1954, Serial No. 429,184

16 Claims. (Cl. 153-25) This invention relates to apparatus and method for forming joggles.

In aircraft construction aluminum eXtrusions are used very extensively. Usually these eXtrusions have, when viewed in cross section, at least one pair of angularly related arms or legs as is the case, for example, with angies, Ts and C-shaped channels. It is often necessary in the building of aircraft to form an offset in these eX- trusions, and the oiset is usually perpendicular to the plane of one of the legs and generally parallel to the plane of the other leg of the extrusion. These olsets are commonly referred to as joggles; and in forming joggles, extreme care must be exercised to prevent buckling of the extrusion in the plane parallel to the direction of the offset or joggle.

Another problem encountered in producing joggles relates to the cost of dies. Heretofore, it has always been the practice to design a particular set of dies for each individual joggling operation. When the number of different joggles and the different sizes of joggles that are required in the construction of a large aircraft are considered, it will be appreciated that the cost of dies for providing all the joggles on a particular job may run into many thousands of dollars.

It is an object of the present invention to provide a novel die assembly for forming joggles designed so that the tendency for the extrusion to buckle or wrinkle in the plane parallel to the direction of joggle is eliminated.

Another object of the invention is to provide a die design which enables the use of a single pair of dies for forming a plurality of diiierent joggles.

A further object of the invention is to provide a basic die arrangement which can be used for forming joggles on a plurality of diierent members by simply replacing one set of die inserts with another set which is shaped to correspond with the cross section of the piece to be joggled. t

In the drawings:

Fig. 1 is an end View of the joggle die assembly of this invention.

Fig. 2 is a sectional View taken along the line 2-2 in Fig. 1 and showing the dies in the closed position forming the joggle in the work piece clamped therebetween.

` Fig. 3 is a view similar to Fig. 2 and showing the dies fin the separated position with the work piece to be joggled positioned to 'be acted upon by `the dies.

Fig. 4 is a top plan view of the bottom die assembly as viewed along the line 4 4 in Fig. 3.

Fig. 5 is a fragmentary detail end View of the arrange- `ment shown in Fig. l with guides removed to better illustrate the assembly.

Fig. 6 is a sectional view taken along the line 6-6 in Fig. 5 and showing the shim for controlling the depth of `joggle formed. Fig. 7 is a sectional view taken along the line 7`7 in Fig. '5.

Fig. 8 is a perspective view of an angle having a joggle formed therein as by the apparatus shown in Figs. 1 through 7.

Fig. 9 is a fragmentary sectional view of the die assembly showing the manner in which the length and depth of the joggle formed may be varied.

Figs. l0, l1 and 12 are fragmentary views generally showing the basic arrangement shown in Fig. 1 as modified for forming joggles on Zshaped, C-shaped and Ti shaped extrusions, respectively.

Figs. 13, 14 and 15 are perspective views of work pieces joggled by means of the apparatus shown in Figs. 10, 11 and 12, respectively.

Referring iirst to Figs. l through 7, the die assembly is shown therein used in connection with a press having a bed plate and a bolster plate (not shown) which the eccentric faces of cams 58.

is movable vertically on guides either by mechanical, hydraulic or other means. The die assembly is arranged to be used in connection with a conventional die shoe assembly which includes a lower die shoe 24 secured to the bed plate 2l) as by bolts 26 and an upper die shoe 28 which is vertically movable on guide pins 30. The lower die unit of this invention includes a pair of die blocks 36 and 3S which are positioned in end-toend relation. (See Figs. 3 and 4). The front die block 36, as viewed in Fig. 3, is secured to the lower die shoe 24 by bolts 40, the heads of which are recessed into the top face of die block 36. The rear die block 38 is supported in normally spaced relation from lower,

die shoe 24 by means of four springs 42 seated in aligned sockets as shown. Headed screws 44 having heads recessed into block 38 are provided for limiting the upward movement of block 38 under the influence of springs 42. Inthe arrangement shown, screws 44 also serve as guide pins for guiding die block 3S in a vertical direction. It desired, dowel pins may be used as guides.

In the arrangement shown in Figs. 1 through 7, die blocks 36 and 33 are formed with longitudinal cut-out portions along opposite edges thereof in. which die inserts are located. The inserts on die block 36 are designated 46 and the inserts on die block 38 are designated 48. These inserts are rigidly mounted on their respective die blocks by cap screws 50. The outer and upper longitudinal faces of inserts 46 and 48 `are machined to receive the work pieces to be joggled. In the `illustration shown in these iigures, the work pieces 52 'are in the form of angles provided with what may be -referred to as a top horizontal leg 54 and a vertical side leg 56 (Fig. 1).

port blocks 460 and are provided with handles 62 for rotating the cams. `wear plate 64 which are mounted on slides 66. Slides The eccentric faces of cams S8 engage 66 are supported for horizontal sliding `movement with reference to support blocks 60 by means of yguide rods 68 which are iixedly supported on slide 66 and extend horizontally therefrom in parallel relation through aligned bores '70 on supports `60. Compression springs 72 `acting between the outer ends of guide rod 68 and supports 60 urge the slides -66 into engagement with It will be noted vthat when the cams are rotated, slides 66 are caused to shift horizontally toward and away from die blocks 36 and 38.

Referring now more particularly to Fig. 1, it will be observed that slides 66 have a notched-out portion at their lower ends for receiving support bars 74 which eX- tend across the full length of slides 66. Bars 74 are mounted on the lower face of slide 66 as by cap screws 76. On each bar 74 there is arranged a pair of clamping bars 78 and 80. Clamping bars 78 and 80 are normally spaced above support bars 74 by a plurality of compression springs 82. Clamping bars 78 and 80 are provided with a dove-tail guide 84 at their adjacent ends, the dove-tail guides 84 being lgenerally transversely aligned with the abutting end faces of die blocks 36 and 38. The bars 78 and 80 are guided for vertical movement on slides 66 by means of gibs 86 mounted at the opposite ends of slides 66 as by screws 88. Screws 88 extend through vertical slots 87 in gibs 86 to permit vertical adjustment of the gibs. `Clamping bars 78 and 80 are formed on their outer end faces with vertical guideways 89 which extend downwardly from the top thereof and terminate above the bottom face of the bars to form stops for limiting the upward travel of the clamping bars. Gibs 86 engage in guideways 89. When the dies are inthe separated condition, clamping bars 78 and 80 extend slightly above the upper face of the horizontal leg 54 of the angles 52 supported on inserts 46 and 48. See Fig. 3. In order to insure perfect rectilinear movement of the slides 66, at each end thereof there is secured on die shoe 24 as by screws 90 a guide plate 92. In Fig. l, the guide plate 92 at the right is shown in full and the guide plate 92 at the left is broken away to show the manner in which bars 74 and 78 are supported on slides 66. In Fig. 5, the assembly is shown with guide plates 92 removed.

The upper die assembly includes front and rear die blocks 94 and 96 respectively. These die blocks are supported on the upper die shoe 28 by means of gibs 98 which are bolted on die shoe 28 by bolts 100. AS will be observed in Fig. l, the front die block 94 includes a mounting member 95 which has a vertical clearance with the ledges 102 of gibs 98 so that the mounting member 9S and die block 94 are guided for vertical movement on shoe 28. The rear die block 96 does not have apclearance with the ledges 102 of gibs 98 and -is therefore rigidly supported on upper die shoe 28. When the upper and lower die shoes are separated, the mounting member 95 rests upon the ledges 102 with the `lower face of die block 94 disposed at a level below the lower face of rear die block 96. Die shoe 28 and mounting member 95 are fashioned with opposed caviyties 104 and 106, respectively, in which a compressible rubber pad 108 is positioned. A shim 110 is secured to the upper face of mounting member 95. The Whole assembly backs up against upper die shoe 28. Mounting member 95 and gibs 98 are formed with interen- .gaged vertical guideways (not shown) for maintaining die block 94 in a longitudinally fixed position relative to lower die block 36.

Assuming that it is desired to form a joggle such as shown at 118 on the angle 52 (Fig. 8), the die arrangement is adjusted for the depth of the joggle by controlling the extent of permissible downward movement of the lower rear die block 38. Thus, in the clearance space between the upper face of die shoe 24 and the lower face ofdie block 38, there is arranged a shim 120 having a thickness such that the vertical distance between the top face of shim 120 and the lower face of die block 38, this distance being designated x, is equal to the depth of the joggle to be formed. Shim 120 is arranged to be inserted beneath die block 38 from the rear end thereof and is therefore suitably slotted as indicated in Pig. 6 to accommodate the screws 44 and springs 42.

It is desirable, especially when joggling relatively thick work pieces, to have both front and back dies bottom at the lower end of the stroke. This insures against bending of the work piece. Accordingly, a shim 121 is `arranged between upper die block 96 and die shoe y28.

Shim 121 is determined in thickness to cause the rear die assembly to bottom at the same instant the front die assembly bottoms. The dies are adjusted for producing the desired length of the joggle by shifting the upper rear die block 96 longitudinally in gibs 98 so that the space y between the rear vertical face of the upper front die block 94 and the front vertical face of the upper rear die block 96 corresponds to the joggle length. With the dies thus adjusted, a work piece or a pair of left and right work pieces are positioned on the inserts 46 and 48. Thereafter, the handles `62 are turned to shift the slides 66 inwardly towards the die blocks 36 and 38. These slides move inwardly to a position where the vertical side legs 56 of the work pieces 52 are clamped laterally against the inserts 46 and 48 by the clamping bars 78 and 80. It will be noted that in this position, the Vertical side legs 56 of the work pieces 52 are supported vertically by the inserts 46 and 48 and laterallybetween the inserts and the clamping bars 78 and 80. Thus, the vertical side legs 56 of the work pieces are supported both vertically and laterally throughout their extent.

Thereafter, the press is actuated to lower the bolster plate. As the bolster plate travels downwardly, it drives upper die shoe 28 downwardly to a position where the lower face of the upper front `die block 94 is brought into clamping engagement with the forward portions of the top faces of the horizontal legs 54 of the work pieces 52, Die blocks 94 and 96 extend laterally over clamping bars 78 and 80. Thus, when die block 94 is lowered to clamp work pieces 52 in inserts 46, it also engages the top faces of clamping bars 78 and moves these clamping bars downwardly to a position where the upper edges thereof are aligned with the upper face of the legs 54 ofthe work pieces v52. Continued downward movement of upper die shoe 28 causes the rubber pad 108 to compress. In the downward movement of die shoe 28', a point is reached where the lower face of the upper rear die block 96 contacts the 4upper face of the portions of the horizontal legs 54 of work pieces 52 which overlie the rear insert members 48. Since die block 96 is rigidly mounted on the upper die shoe 28, continued downward movement of die shoe 28 causes further compression of pad 108 and also causes the lower rear die block 38 to move downwardly and thereby compress springs 42. When die block 38 contacts shim 120 (Fig. 2), the portions of the horizontal legs 54 of work pieces 52 which overlie the rear inserts 48 have been shifted downwardly relative tothe portions of these legs which overlie the front inserts 46 `an extent corresponding to the depth of joggle desired. Thus, the joggle 118 is formed on the work piece 52; and the portion of the vertical leg 56 which isadjacent the joggle 118 is at all times supported laterally and is thereby prevented from buckling or wrinkling.

It is to be noted that shim is controlled in thickness such that when die block 38 bottoms against shim 120, die block 94 with its mounting member 95 and shim 110 bottoms up against die shoe 28. Thus, both sets of dies are arranged to bottom against solid supports. This eliminates the tendency for the work piece to twist or to shift while clamped between dies 94 and 96.

IIt will be observed that if it is desired to form a joggle in another series of work pieces 52 having a depth and ,length different from the joggle 118, it is merely necessary to replace the shim 120 with another shim 122 of the required thickness to obtain the desired depth of arrangement of Figs. 1` through 8, the shim 123 being thinner than shim 122.

From the die arrangement thus far described, it will be readily apparent that the same basic die assembly may be used for forming joggles in differently shaped work pieces by substituting only a few of the members shown in Figs. 1 through 9 for other members adapted to accommodate the particular work piece which it is desired to joggle. For example, in Fig. there is illustrated an arrangement for forming a joggle 124 in a Z- bar 126 as shown in Fig. 13. The assembly is shown in Fig. 10 as viewed from the opposite end shown in Fig. l. The only modification in the assembly resides in replacing the front and rear inserts 46 and 48 respectively with other inserts shaped to accommodate the Z- bars 126. The rear inserts are designated 128 in Fig. 10. In addition, auxiliary inserts are secured to front and rear clamping bars 78 and 80. The latter inserts for the rear clamping bars 8@ are designated 130. In other respects, the general die assembly and its operation is substantially as shown and described with reference to Figs. l through 9. When the joggle is formed, the horizontal leg 132 is held clamped between the lower face of die block 96 and the other horizontal leg 134 is clamped between the lower face of the insert 130 and the lower stepped face of insert 128. The vertical leg 136 of the work piece is clamped laterally between the side face of insert 130 and the side face of insert 128. It will be appreciated, of course, that in Fig. l0, only the rear end of the assembly is shown; and reference is therefore not `made to the front insert members which mate with inserts 128 and 13). It will be appreciated, however, that these mating insert members together with the die blocks 96 and 38 at the rear of the assembly and the die blocks 94 and 36 at the front of the assembly support the work piece 136 throughout its extent both vertically and laterally. Therefore, there will be no wrinkling or buckling of the vertical leg 136 of the work piece. It will be observed that vertical guideways 89 on clamping `bars 78 and Si) permit inserts 130 to shift upwardly to a position free of the vertical ange 135 on the horizontal legs 134 of the work piece so that the inserts 130 can be brought into and out of clamping engagement with the work piece.

In Fig. 1l, there is illustrated a die arrangement for forming a joggle 138 in a C-shaped extrusion 140. As in Fig. 10, only the rear end of the die assembly is shown. In this case, the upper `die shoe 142 is provided with grooves for accommodating the upper `curved portion of the member 140; and the rear inserts 144 are likewise shaped to accommodate the work pieces. With this arrangement, as is true in Fig. l0, the same lower die blocks 36 and 38 may be employed as in the arrangement illustrated in Figs. l through 9. Likewise, the clamping bars "78 and 80 employed in the arrangement illustrated in Figs. l through 9 are utilized. As in the prior modifications described, the C-shaped extrusions 140 are supported laterally and vertically throughout their extent at least at the portion of the work piece wherein the joggle is formed to prevent buckling of the side wall 146 of member 148.

The arrangement shown in Fig. 12 is utilized in forming a joggle 148 on a T-shaped extrusion 158. In this arrangement, the upper dies 94 and 96 :are the same as used in connection with the arrangement shown in Figs. l through 9. The clamping bars '78 and 80 are also employed. These clamping bars have front and rear spacers secured thereto, the rear spacers being Vdesignated 152. VOne set of spacer bars, those shown `at the right of Fig. l2, have also mounted thereon front :and rear inserts, the rear insert being shown and desig- -nated 154. Another pair 4of inserts, the rear one being `designated 156, are mounted on the bottom die block being designated 15S. These inserts are fashioned to provide a seat for thei`T-shaped extrusion 150 which supports the vertical wall 156 thereof both laterally `and vertically so that when the joggle 148 is formed therein, the wall 156 will not buckle or wrinkle adjacent the joggle.

Except as is noted in the foregoing description, the arrangements shown in Figs. 10, 1l and l2 are the same as that shown in Figs. 1 through 9 both in operation and in the adjustments. Since these arrangements are basically all the same except for the dierences required to accommodate different Work pieces, the showing in Figs. l0, ll and l2 illustrate the assembly as viewed from the rear end only. In each case, the upper die block shown is rigidly secured to the upper die shoe 28 with the shim 121 interposed therebetween and the lower die block is mounted for vertical movement on the lower die shoe 24, its movement in the downwardly direction being limited by the shim 120.

Thus, it will be seen that the present invention provides a die arrangement for forming joggles which` make for economy, ease of operation and the production of smoothly formed joggles without wrinkling.` In addition, it will be noted that if the material being worked is such as to require heating before joggling, the work pieces may be heated while in the dies by simply inserting heating elements (not shown) in sockets formed in the die blocks to receive such heating elements.

I claim:

l. A die assembly for forming joggles in work pieces having a pair of longitudinally extending angularly 'related legs 4comprising `a lower support, an upper support movable vertically toward and away from said lower support, a pair of axially aligned die blocks on said lower support, a pair of axially aligned but spaced apart die blocks on said upper support positioned above the `die blocks on said lower support, one die block in each pair being guided for vertical movement on its support and the other die block in each pair being fixedly mounted `on its support, said movable upper die block being biased downwardly, said movable lower die block being biased upwardly whereby said last two mentioned die blocks are normally spaced vertically from their respective supports, the movable die block on each support being vertically aligned with the iixedly mounted die block on the other support, means on said lower die blocks for supporting said work piece with one leg thereof in a generally vertically disposed position and with one face of said last mentioned leg exposed and said lower support having a generally horizontal supporting surface, a clamping member on said surface of the lower support movable in a generally horizontal plane into clamping engagement with the exposed face of the vertically disposed leg of the work piece supported on said lower die blocks, said clamping member comprising two sections positioned end to end in generally transverse alignment with said two lower die blocks, the section of said clamping member aligned with said vertically movable lower die block also being guided for vertical movement on said lower support.

2. A die assembly as called for in claim l wherein both sections of said clamping member are guided for vertical movement on said lower support.

3. A die assembly as called for in claim 2 including means biasing said two sections of said clamping member upwardly on said lower support to a position where the upper face of the clamping member is normally dis,- posed above the upper face of said lower die blocks.

4. A die assembly as called for in claim 3 wherein said upper die blocks overlap said clamping member.

S. A die assembly as called for in claim 4 including a support block movably mounted on said lower support `and supporting said clamping member, means guiding said support block for rectilinear movement along a line extending normal to the longitudinal axis of said lower die blocks.

6. A die assembly as called for in claim 5 including a rotatable cam member for moving said support block along said line in a direction toward said lower die blocks. 7. A die assembly for forming joggles in a work piece having a pair of longitudinally extending, angularly related legs comprising a lower support, an upper support vertically movable toward and away from said lower support, a pair of axially aligned die blocks on said lower support, a pair of axially aligned die blocks on said upper support positioned directly above said lower die blocks, one die block in each pair being guided for vertical movement on its support and the other die block in each pair -being xedly mounted on its support, said movable upper die block being biased downwardly and said movable lower die block being biased upwardly, a shim between the lower support and the lower movable die block for limiting the downward movement of said movable lower die block to a distance less than the permissible upwardly movement of said upper movable die block, a shim between said upper support and the upper fixed die block, the movable die block on one support being vertically aligned with the xedly mounted die block on the other support, means on said die blocks for supporting a work piece thereon with one of said legs disposed generally vertically, the combined thickness of said two shims being such that the movable lower die bottoms on the lower support when the movable upper die bottoms on the upper support whereby the depth of the joggle can be varied without changing the travel of the upper support by replacing said two shims by another set of the same combined thickness but individually of diierent thickness.

8. A die assembly for forming joggles in a work piece having a pair of longitudinally extending, angularly related legs comprising a lower support, an upper support vertically movable toward and away from said lower support, a pair of axially aligned die blocks on said lower support, a pair of axially aligned but spaced apart die blocks on said upper support positioned directly above said lower die blocks, one die block in each pair being guided for vertical movement on its support and the `rother die block in each pair being ixedly mounted on its support, said movable upper die block being biased ,downwardly and said movable lower die block being biased upwardly, means for limiting the downward movement of said movable lower die block to a distance less than the permissible upwardly movement of said upper movable die block, the movable die block on one support being vertically aligned with the tixedly mounted die block on the other support, and means on said die blocks for supporting a work piece thereon with one of said legs disposed generally vertically and means movable in a generally horizontal plane for clamping said vertically extending leg laterally against said lower die blocks, said lower die blocks being provided with aligned longitudinally extending recesses at one side thereof, said recesses extending upwardly to the upper face of said die blocks, die insert members removably secured in said recesses, said die inserts having a seat thereon for supporting the work piece, said inserts each being provided `with a side face, the upper portion of which is inwardly offset from the lower portion thereof and separated therefrom by a longitudinally extending, horizontally disposed shoulders, said inwardly oiset side face portion being dimensioned to receive one leg of said work piece with said shoulder supporting said one leg vertically and said inwardly offset side face portions supporting said leg laterally, said clamping means comprising a clamping member on said lower support movable transversely of said lower die blocks into clamping engagement with the exposed face of the leg of said work piece supported on said shoulder, said clamping member comprising two sections positioned end to end, said sections being aligned transversely one with each of said lower die blocks, the section of the clamping member which is transversely aligned with said movable lower die block being movable u vertically on said lowerfsupport and being biased up-` wardly from said lower support. l

9. A die assembly as called for in claim S wherein said upper die blocks overlap said clamping member.

10. A die assembly as called for in claim 9 including a supporting block movably mounted on said lower support and supporting said clamping member, both sections of said clamping member being mounted on said support block for vertical movement thereon and means biasing said sections in an upwardly direction on said support block,

11. A die assembly as called for in claim 10 wherein one of the adjacent ends of said sections is provided with a vertical guideway therein and the other of the adjacent ends is provided with a vertically extending rib seated in said guideway.

12. A die assembly for forming joggles in a work piece having a pair of longitudinally extending, angularly related legs comprising a lower support, an upper support vertically movable toward and away from said lower support, a pair of axially aligned die blocks on said lower support, a pair of axially aligned but spaced apart die blocks on said upper support positioned directly above said lower die blocks, one die block in each pair being guided for vertical movement on its support and the other die block in each pair being ixedly mounted on its support, said movable upper die block being biased downwardly and said movable lower die block being biased upwardly, means for adjusting the extent to which said lower movable die block is permitted to move in a downwardly direction, the movable die block on one support being vertically aligned with the tixedly mounted die block on the other support and means on said die blocks for supporting a work piece thereon with one of said legs disposed generally vertically, said last mentioned means comprising a clamping member mounted on said lower support independently of and normally spaced from the die blocks on the lower support, said clamping member comprising two sections placed end to end and aligned generally one with the iixedly mounted lower die block and the other with the vertically movable lower die block, the latter section being guided for vertical movement, and means for moving said clamping member into clamping engagement with said vertically disposed leg of the work piece.

13. A die assembly as called for in claim 12 wherein said adjusting means comprises a shim removably positioned between said movable lower die block and said lower support.

14. A die assembly as called for in claim 13 including a shim removably arranged between each of said upper die blocks and said upper support.

l5. A die assembly as called for in claim 14 wherein the overall vertical dimensions of the two sets of vertically aligned die blocks and shims are equal such that that the lower movable die block bottoms on the lower support when the upper movable die block bottoms against the upper support.

16. A die assembly for forming joggles in a Work piece having a pair of longitudinally extending, angularly related legs comprising a lower support, an upper support vertically movable toward and away from said lower support, a pair of axially aligned die blocks on said lower support, a pair of axially aligned but spaced apart die blocks on said upper support positioned directly above said lower die blocks, one die block in each pair being guided for vertical movement on its support and the other die block in each pair being xedly mounted on its support, said movable upper die block being biased downwardly and said movable lower die block being biased upwardly, means for limiting the downward movement of said movable lower die block to a distance less than the permissible upwardly movement of said upper movable die block, the movable die block on one support being vertically aligned with the iixedly mounted TRM die block on the other support, means on said die blocks for supporting a work piece thereon with one of said legs disposed generally vertically, and means movable in a generally horizontal plane for clamping said vertically extending leg laterally against said lower die blocks, said clamping means comprising a clamping member on said lower support movable transversely of said lower die blocks into clamping engagement with the vertically disposed leg of the work piece, said clamping member comprising two sections positioned end to end, said sections being aligned transversely one with each of said lower die blocks, the section of the clamping member which is transversely aligned with said movable lower die block 10 being movable vertically on said lower support and being biased upwardly from said lower support.

References Cited in the le of this patent UNITED STATES PATENTS 

